Process of and apparatus for heating.



F. FISCHER.

PROCESS or ND APPARATUS FUR HBATmG.-

APPLIUATIOI FILED OCT.6, 1913.

Patented Juhe 9, 1911i.

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i I' .Jl-mamm-ma...hummm-numana"m entren srafrns PATENT oFFIoE.'

` FRANZ FESClE-R, 03E' CHARLOTTENBURG, GERMANY.

PROCESS 03F AND APPARATUS FR HEATING.

Specication of Letters Patent. l Patented June 9, 1914, Applicationfiled October 6, 1913. Serial 110.793,691.

or, and more frequently, full of what is virtually products ofcombustion; the air 'reacting with carbon or carbonaceous material whichis practically always present, and which may occur in the form a mixtureof carbon dioxid and nitrogen'. Apart from the chemical properties ofthe air or products of combustion, and both are freely oxidizing to mostAof the metals, an atmosphere of this character has the disadvantagethat it does not carry heat quickly. A. vacuum, which is sometimes 'ball whom t may concern.: v

Be it known that I, Dr. FRANZ FISCHER, a subject of the Empire ofGermany, residing at Charlottenburg, in the Empire of Germany, haveinvented certain new and useful Improvements in Processes ofand-Apparatus for Heating, of which the following is a specification. A

This invention relates to rocesses of and apparatus for heating; an itcomprises a process of heating wherein an object of any material, suchas metals, plastic 'ceramic material, etc., is heated by beingmaintained in an atmosphere of hydrogen, or 'of gas rich in hydrogen, inproximity to a metallic or other heating element through which a heatingcurrent passes, the relative location otthe tivo being such thatcirculation of hydrogen therebetween is uniinJede/(Land such hydrogenbeing protectedagaist cooling; and it further comprises an electric`:furnace having a/closed chamber. of refractory material provi-ded withinterorly disposed heating elements or resistors et metal or thelilreand adapted to support material to be heated located in proximitythereto and Without intervening Walls or jacketing elements for theresistors tc impede ltransmission of heat between, the heating clementeand such material and means for sugoj4 plying hydrogen orgas rich inhydrogen to the interior of 'the chamber; alliV as more fullyhereinafter set forth land as claimed.

In the customary methods of heating by usual to heat a Wall orOrdinarily the development of heat is, at least in part, above the thingto be heated and communication of heat thereto is therefore, to thisextent, against convection. Air and products o combustion are poorconductors of heat, either by sheer conduction, 'by convection or bydiiusion. Nitrogen is like air.

ln practice, operating with steel jacketed furnaces having Wall-embedded resistors, and'particularly,with large furnaces, it is foundthat at temperatures such as 1000o C. and beyond, the jacketsof the whenprotected with an exterior layer of iircclay or other refractorymaterial, are de- .stroyeu in a short time by oxidation. The resistancecoils which are embedded in the refractory n'iaterial and communicateheat to the interior of the furnace through the intervening layer' ofrefractory material also communicate heat to the outer jacket heatingelements, to

used to avoid oxidation phenomena, isgof course still Worse'as regardscarrying heat.'

furnaces, even electrical energy it is Walls of the heating chamber andimpart m the same Way. In the' present invention heat thence to theobject to be heated, the. these difficulties are obviated and a number lradiation from such Walls being relied on of new advantages secured bylocating the .tor the conveyance of heat to a greater or resisting orheat-developino elements With- 40 le* extent, Frequently, Wires 0f4somo, re- 11i the funaCe Chamber itself instead vOf .tractory metal,such as platinum, tungsten, within its Walls and atany distance rfromnichel-chromium alloys, etc., are embedded the Walls that may bedcsired,'and by emin the refractory lining ot' a steel cased ploying hydrogen,or a gas rich-infz'ee hychamber near its inner wall surface, thisdrogen, as the means for conveying the 45 embedding being to protectsuch Wires from heat from the resistor to the object to be the action otthe chamber atmosphere. The heated. The walls in'lieu of being heat-im-Wire 'then' gives heat to the lining and the parting elements areheat-retainingv or heatlining to the chamber. Sometimes the wall,insulating elements. Advantageously'naled which is then usually ofgraphite, is'itse'lf the resistor Wires are placed in the chamber at 5cresisting and y heat-generating 'element a relatively low level. Ashydrogen has no Apart troinother circumstances, this 'wall oxidizing orotherv detrimental-influence, heating is disadvantageous in that itlimits upouxmetals at a high temperature, the locajthe size of tlechamber since radiative heattion of a naked resistor Within the fur-ling diminishes rapidly in efficiency with an .nace hamberis notvdisadvantageous and in 55 increase` in chamber size. The heatingpracticeit may be ylacedi' suchproximity chamber .is usually maintainedfull of air, tothe object to be-,meatedtasfay'be desired.

Advantageously, it is spaced somewhat away from the wall although in thecase of a cylindrical Wire, or acoileu wire, it may touch the saine. Theless, however, the area contacting With the Wall, the greater is thearea exposed to hydrogen and the more the advantages of the presentinvention are Secured. lt is therefore lest to space them away from thewall as inuch as possible. Hydrogen has a very high rate of conductionfor heat, and particularly at high temperatures, and it also has a highrate of diffusion and of convection. Roughly, the rate of dillusion ofhydrogen is only a little less than four times as fast as the rate ofdidnsion of air. VV' ith this high heat-conveying capacity of hydrogento exercise a. cooling effect, resisto-1' wires bathed in hydrogen may,be safely run with much more current than would be feasible With thesaine Wires in contact with air,rWith refractory material, or withanother gas than hydrogen; or, what is the same thing, for the sameamount of heat developed less wire need be used.

It is agrcat advantage of the present invention that resistors may besafely run at' temperatures but little below those at which the metal-or' the resistor would yield, allowing development of highertemperatures; and that with a given wire theobject to be heated-n'xay bebrought to a temperature-very nearly that developed in the Wire; i. e.,the object may be heated hotter with such Wire than in the usual Ways ofheating with the same wire. lith resistor Wires as usually employed, inview of the necessity for shielding them against the attack. of theordinary atmospheres and the bad heat conductivity oi air, nitroe'en,vacuum, etc., and the consequent necessity for rely-ing largely onradiation-toi.' conveyance ol? heat, ordinarily the res tors must'be runat 'a much higher temperature than that intended to be imparted to thearticle to beheatcd; there must be a comparativcly large temperaturediffer-enf tial between tie heating eleincrit and the thing to beheated. lu, the present invention becauseI ofthe high capacity ofhydrogen lor rmreivingalul imparting heat, the tem-- lwraturediiferential between the, resistance element-and the thing to be heatedcan be much lessened. `This resul in an economy of material and ofenergy. And since no attempt is made to utilizo the walls asheatradiating or Yhems-imparting elements, reliance being placed on theheat conductivity of hydrogen, the naked resistors may be locatedanywhere vwith'in'the heating chamber, and in any spaceddistributiondesired, thereby enabling the use ofheatiug chambers of anysize.,l3utlit is best to place them near the Hoor of the chan'ibe'r. Anadvantageous arrangement is toplace a eoil of Wire around thechamber-just above the' Hoor and near the side walls. Since the heat'isnotdevel` oped in the Wall, the jackets do not suller in the usual way;and ruoremfer any type ofv lining or of interior heat insulation may beemployed'. lVater jackets for the exterior of the furnace may be used.

The resistors may be of any of the high melting met .ls such asplatinum, tungsten, tantalum, `-:el alloys, chromium alloys, etc., sincethese metals are all permanent in hydrogen. The greater the free spacefilled with hydrogen surrounding the resistors, the greater is theamount of current which can be sent through them and the greater can bethe development of heat per second Without the risk of raising the metalto a temperature sufficient to endanger it. The conduction, andcommunication of heat by hydrogen is, so rapid that as lon as coolerobjects are in the vicinity', it is di cult to overheat a wire bathed inhydrogen and out of Contact with a heat retaining surface. 'Acomparatively small naked resistance Wire in and freely exposed to anatmosphere of hydrogen Will suffice to bring up to approximately its owntemperature a neighboring, comparatively large object to be heated.lWhile l regard the arrangement of resistors and to be heated shown inthe accompany/1 trations to be highly advantageous, any otherarrangement may be usedwvhich utilizes the principles herein s'et forth.While it is best to use pure hydrogen in order to secure a maximum ofthe results sought, I may use other gases' rich in free hydrogen, as forinstance ordinary blue gas (uncarbureted water gas). But a gas rich inhydrogen and free from carboni monoxid or carbon dioxid is better.Electrolytic hydrogen or vhydrogen made with iron may be used. Thehydrogen may be introduced and removed as a continuous current, butthere is ne particular object in the present invention in making thiscurrent a lively one unless reduction as well as heat-ino' be desired.It suffices to introduceenough vto replace the original atmosphere ofthe chamber and to compensate for accidental leal:- age, dilusion, etc.

'lhe object to be heated maybe of any shape, size or character, and maybe of any material, such as ceramic material, metal, etc. Materialswhich are readily reduced by hot hydrogen will of course undergo otheractions than those here desired, the heating being-attended byreduction. The articles to he'heated may be supported on supports of anysuitable refractory7 material, such, as

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sand, iireclay, titanium oxid, etc., or may bei located directly on thechamber Graphite and other forms of carbon may be employed as supportsfor the article, an indeed may even be employed as resistors, since atmost of the temperatures contemplated in the use of the electricfurnace, the hydrogen has no particular action upon carbon. At a,

oor.

very high temperature however methane may form and be again broken upwith pro duction of sooting. rdinarily I prefer to have the furnacechamber free of carbon in any form.

It must be remembered in designing apparatus embodying the resentinvention that the high heat conductivity of hydrogen means a very evendistribution of heat throughout the heating chamber, and that it isdifiicult' to attain therein any local high heat-ing such as is commonwith chambers lled with other gases. Ordinarily therefore the designshould be suoli as to have as little chamber space unoccupied by heatdeveloping elements and material to be heated as possible; in otherwords, it is inadvisable to have the chamber larger than is required forthe needs of the heating operation to be carried out. Circulation ofhydrogen between the resistors and the material must however beunimpeded by intervening objects or Walls. Chambers of indefinite sizemay be employed under the larger the chamber the more heat must beintroduced into it, since, as stated, heating throughout the chamberwill be very nearly uniorm. Because ofthe of hydrogen and the speed withwhich it escapes through all cracks and porcs, it is necessary to havethe chamber as tight as possible and to have eilicient sealing means forthe doors9 etc. Vlater cooled elements may be used lto secureeicientjoints. The high heat conductivity of hydrogen also necessitutesas good heat insulation as may be of the containing chamber.

In the accompanying illustration I have shown, more or lessdiagraniniatically, an embodiment of apparatus elements within thedescribed invention and capableof vuse in the described process.

In this showing Fig'g'ure 1 is a central Verticai section of a heatingchamber; F ig. 2 is a horizontal section along line cc--m of Fig. l; andFig. 3 is a vertical section of Fig. l at right angles to the showing ofFig. 2, and along line y-y/.

In this showing, furnace chamber l is constituted by an open endedcasing 2 of mag-l nesia. fircbriclr, or other suitable refractory andheal-inslating material capable of 'withstanding the temperatures to beem ploycd. A steel jacket 3 gives the necessary strength. the roof inletpipe 4 is provided for the introductionl of hydrogen. This pipe maybemperforated at intervals. Asi-shown, tlieront of the furnace is open.At this point it may be provided with a Water jacket casing 5surrounding it.V Fitting in the end o? the chamber is a door havingdistance a. distance which. ma f be e uivalent the present inventionbutl ready ditusibilityprojecting portion, or block 6 of rel fractorymaterial extending inwardly-some extends on the furnace. This block fitsas nearly as may be against the interior walls of the furnace. It iscarried on an iron plate 7 which may carry a gasket 8 of rub. ber or thelike adapted to make a ti ht joint against the waterjacke't casing. T eplate is cooled by a' Water jacket 9. Extending through a body ofinsulating material 10 in the water jacket are two current leads 1l- 11.Within the furnace chamber is resistorA Wire 12. shown as lying in thecorner vformed by the bottom of the chamber and the side Wallsand asencircling the\chamber. This is convenient and allows the greaterportion of the door of the furnace to be unobstructed.

In the use of the above structure, the material to be heated or treatedhavin been placed in they furnace either on the ior or on a suitablesupport, the door is placed iniposition with a loose fit and hydrogen,or hydrogen containing gas, is introduced through 4 until the air issubstantially displaced. The door is now laced in such sition as to makea tight gun by sendingasuitable current through the resistor 12trom-current leads 11. Water is kept circulating through amount as maybenecessary. ABy placing the resistors outside the casing wall'and spacedaway therefrom, annoyance and in-4 convenience by conduction of currentthrough the refractory materiall itself is avoided. Most refractorylmaterials used for lining furnaces become second-class conductors athigh teriperatures 'and it is difficult to insulate a resistor againstyloss of current in this way.

1. ln the art of heating, the process which comprises maintaining anobject to be heated in proximity to an electrically heated metallicresistor element in a suitable chamber full of hydrogen, said resistorelements being bathed in said hydrogen and said` chamber havingl Wallsof heatlretaining material at all surfaces exposed t`o said hydrogen.

2. In the art of heating, the process which comprises maintaining auobject to be heated in proximity to heated wire, both said object andsaid Wire being bathed in and surroumlcd by an atmosphere of hydrogencontained in a chamber of low heat conductivity.

3. In the art of heating, the processwhich comprises placing a body tobe heated within a chamber having all interior walls of refractory,heat-retaining material, filling said' chamber with ing electrical heatin a resistor bathed by said hydrogen.

4. In the vart of heatingLthe process which comprises placing a body 'tbbe heated witht and heating bi;-A4

:in electrically hydrogen and produc- 'l in a chamber having allinterior Walls of rc- 7 fractory, heat-retaining material, filling lsaid chamber with hydrogen, and producing chamber with Aall interiorwalls of refrac-` tory,` heat-retaining material, means for supplying.hydrogenI to the interior of the chamber y and resistor elementsdisposed Within said 'chamber and interiorly beyond said Walls."

. 7. In an'electric furnace, a metal jacketed chamberhav-ingr interiorWalls of i" 1"ractory` heat-retaining material, means for introducinghydrogen in said chamber, resistor elements Within said chamber at a 10Wlevel and interiorly beyond said Wall and a `closure of refractorymaterial for said chamber.

8. In an electric furnace, a metal 'acketed chamber having' interiorWalls of re ractory,

heat-retaining material, means for introducing hydrogen 1n said chamber,resistor elements within sald chamber at a loW level and interiorlybeyond said Wall, a closure of refractory material for said chamber andWater jacketed sealing elements for said closure. v

- In testimony whereof, I aiiX my signature in the presence of twosubscribing Witnesses. Dn. FRANZ FISCHER.

'Vitncsses vvVoLDi-JMAR HAUrT, HENRY HAsrnR.

